1. Field of the Invention
The present invention relates in general to the release of volatile substances and, more particularly, to a device for controllably releasing volatile substances in their vapor phase to the surrounding atmosphere.
2. Background Art
Devices for delivering volatile substances from a container, as a liquid, to the atmosphere, as a vapor, have been known in the art for several years. In particular, many of these devices make use of the principle of diffusion. For instance, some devices make use of a wick based system. In these systems, one end of a wick is placed in a fluid to be dispensed, while the other end is exposed to the atmosphere. Capillary action forces liquid through the wick and up to the exposed end, where the liquid evaporates off of the end of the wick and into the surrounding atmosphere.
Other devices make use of a gravity driven mechanism, allowing liquids to diffuse through a membrane under the force of gravity. For instance, Zembrodt, U.S. Pat. No. 4,948,047 shows a container for holding a liquid reservoir which is in contact with a membrane positioned in the bottom of the container. Under the force of gravity, the liquid diffuses through the membrane and volatilizes into the surrounding atmosphere from the exposed surface of the membrane. Likewise, Munteanu, U.S. Pat. No. 4,917,301, discloses a similar container for housing a liquid, with a membrane in the bottom of the container. Gravity again forces the liquid to diffuse through the membrane, from where it then evaporates into the surrounding atmosphere.
Although these and other conventional controlled delivery systems have worked well, they have failed to provide for both the controlled and constant release of fluids over an extended period of time. It is a well known goal in the art to increase the linearity of the release of fluids from delivery devices. Moreover, the prior art devices have traditionally been inefficient as they have failed to deliver substantial portions of the fluid contained in the fluid reservoir, thus losing the remaining fluid when it is discarded. Finally, such devices have failed to provide a means for a user to control the rate of release of fluids to the surrounding atmosphere, a desirable feature as different users enjoy different concentrations of the volatilized substance in the air.
The present invention comprises a device for controllably releasing volatile substances from a housing. The controlled substance release device comprises a housing, a volatile substance, and a means for controllably releasing the substance from the housing. The housing further consists of an interior region, an opening in the bottom end of the device, and means for orienting the device so that the force of gravity maintains the volatile substance over the opening the bottom end of the device.
In one preferred embodiment, the device further consists of a porous plug, which functions as the controlled release means. The plug is positioned within the opening in the bottom of the device, and is in contact with the volatile substance. At the same time, at least a portion of the bottom surface of the plug is exposed to the atmosphere to allow the volatile substance to evaporate from the plug into the surrounding atmosphere. In addition, the device may further consist of a means to re-supply the housing with additional volatile substance. Such a re-supplying means may consist of an independent top end to the device, or an inlet port through which the volatile substance may be poured. Moreover, it is also contemplated that the volatile substance may be contained in a replaceable cartridge having means to cooperate with the housing during use of the device, to, in turn, allow the volatile substance to be released from the cartridge.
In another preferred embodiment, the device further consists of a porous plug and the housing being constructed of a material which is substantially permeable to ambient air, yet substantially impermeable to the volatile substance contained within the housingxe2x80x94in combination functioning as the controlled release means. The housing consists of a series of microscopic pores, and may be fabricated from polypropylene, high density polyethylene, and polyethylene, to name a few. The housing allows ambient air to enter the interior region of the housing, thus allowing the volatile substance to diffuse through the porous plug at a constant and linear rate. At the same time, the housing prevents any loss of the volatile substance from the housing walls, through, for instance, a vent, thus preventing uncontrolled loss of the volatile substance through passages other than the porous plug.
In still another preferred embodiment, the device further comprises a means to control the amount of ambient air that enters the interior region of the housing, thus controlling the release rate of the volatile substance from the device. Such a means consists of a housing that is substantially permeable to ambient air, yet substantially impermeable to the volatile substance, and a shell that obstructs at least a portion of this ambient air permeable housing. The shell may be adjusted relative to the housing to, in turn, control the diffusion rate of the volatile substance through the porous plug and thus the release rate of the volatile substance from the device.
In yet another preferred embodiment, the device further comprises a porous plug and an electrochemical gas generating cell, which act to control the rate of release of the volatile substance from the housing. The cell emits gases into the interior region of the housing, thus allowing constant release of the volatile substance through the porous plug and into the surrounding atmosphere.
In still another preferred embodiment, the device further consists of a first porous plug positioned within the opening in the bottom of the device and at least partially exposed to the ambient atmosphere, a second porous plug positioned in contact with the volatile substance, and an air gap between the two plugsxe2x80x94in combination forming the means for controllably releasing the volatile substance from the housing. In operation, the volatile substance diffuses through the first porous plug and enters the air gap between the plugs in a substantially vapor form. The vapor then diffuses, either remaining in a vapor form or returning to its liquid form, through the second porous plug, before entering the surrounding atmosphere.
In another preferred embodiment, the device further comprises an opening formed in the housing, which is positioned below the volatile substance, and an emanator pad, which is positioned below the openingxe2x80x94the controlled release means in this embodiment. The volatile substance drips through the opening, where it falls onto the emanator pad. The emanator pad, in turn, absorbs the volatile substance, before the substance volatilizes from the surface of the emanator pad into the surrounding atmosphere.
In still another preferred embodiment, the device further consists of a heating element, which increases the evaporation rate, and thus the release rate of the volatile substance.